Wiring circuit board

ABSTRACT

A wiring circuit board includes a metal support layer, a base insulating layer disposed on one side in a thickness direction of the metal support layer, and a conductive layer disposed on one side in the thickness direction of the base insulating layer, and including a first terminal and a ground lead residual portion electrically connected to the first terminal. A thickness of the ground lead residual portion is thinner than a thickness of the first terminal.

TECHNICAL FIELD

The present invention relates to a wiring circuit board.

BACKGROUND ART

Conventionally, a wiring circuit board has been known including a metalsupport board, a base insulating layer disposed on the metal supportboard, and a conductive pattern disposed on the base insulating layer,and in which the conductive pattern includes a wiring pattern forelectrically connecting two terminals, and a ground pattern forelectrically connecting the terminal to the metal support board.

In such a wiring circuit board, there is a case of forming anelectroless plating layer on the surface of the conductive pattern.However, a deposition rate of the electroless plating on the wiringpattern, and a deposition rate of the electroless plating on the groundpattern are different due to the presence or absence of electricalconnection between the patterns and the metal support board, and it isdifficult to form a uniform electroless plating layer on the conductivepattern.

Therefore, a method for producing a wiring circuit board has beenproposed in which together with the wiring pattern and the groundpattern, an extension pattern for electrically connecting a terminal ofthe wiring pattern to the metal support board is formed, an electrolessplating layer is formed on the surface of the wiring pattern and thesurface of the ground pattern, and thereafter, by removing the extensionpattern, the wiring pattern is insulated from the metal support board(ref: for example, Patent Document 1).

CITATION LIST Patent Document

-   Patent Document 1: Japanese Unexamined Patent Publication No.    2010-171040

SUMMARY OF THE INVENTION Problem to be Solved by the Invention

However, in the method for producing a wiring circuit board described inPatent Document 1, since the extension pattern has the same thickness asthe terminal of the wiring pattern, there is a problem that it takestime to remove the extension pattern. Further, when the extensionpattern is removed by etching and the like, there may be case where theterminal is eroded by over-etching, and the connection reliability ofthe terminal decreases.

The present invention provides a wiring circuit board capable ofimproving the connection reliability of a terminal portion, whilecapable of forming a uniform electroless plating layer on a conductivelayer, and a method for producing a wiring circuit board havingexcellent production efficiency.

Means for Solving the Problem

The present invention [1] includes a wiring circuit board including ametal support layer, an insulating layer disposed on one side in athickness direction of the metal support layer, and a conductive layerdisposed on one side in the thickness direction of the insulating layer,and including a terminal portion and a ground lead residual portionelectrically connected to the terminal portion, wherein a thickness ofthe ground lead residual portion is thinner than a thickness of theterminal portion.

However, in the production of the wiring circuit board, the ground leadresidual portion is formed by removing a portion of a ground lead forelectrically connecting the terminal portion to the metal support layer.Therefore, before the ground lead is removed, since the terminal portionis electrically connected to the metal support layer, it is possible touniformly form an electroless plating layer on the conductive layer.

Further, according to the above-described configuration, the thicknessof the ground lead residual portion is thinner than that of the terminalportion. Therefore, as compared with a case where the thickness of theground lead residual portion is the same as that of the terminalportion, it is possible to smoothly remove the ground lead. Further,when the ground lead is removed by etching and the like, it is possibleto suppress the erosion of the terminal portion by over-etching, and toimprove the connection reliability of the terminal portion.

The present invention [2] includes the wiring circuit board described inthe above-described [1], wherein the terminal portion includes aplurality of terminal forming layers laminated in the thicknessdirection, and the ground lead residual portion includes a lead forminglayer continuous with at least one of the plurality of terminal forminglayers.

According to such a configuration, since the terminal portion includesthe plurality of terminal forming layers, and the ground lead residualportion includes the lead forming layer continuous with the terminalforming layer, it is possible to reliably make the thickness of theground lead residual portion thinner than that of the terminal portion.

The present invention [3] includes the wiring circuit board described inthe above-described [1] or [2], wherein the ground lead residual portionis located in an end portion of the wiring circuit board.

According to such a configuration, since the ground lead residualportion is located in the end portion of the wiring circuit board, inthe production of the wiring circuit board, it is possible to moresmoothly remove a portion of the ground lead, and to form the groundlead residual portion.

The present invention [4] includes the wiring circuit board described inany one of the above-described [1] to [3], wherein a portion of theinsulating layer protrudes toward the opposite side of the terminalportion with respect to the ground lead residual portion and the metalsupport layer in a direction in which the ground lead residual portionextends.

According to such a configuration, since a portion of the insulatinglayer protrudes toward the opposite side of the terminal portion withrespect to the ground lead residual portion and the metal support layer,it is possible to reliably insulate the ground lead residual portionfrom the metal support layer.

The present invention [5] includes the wiring circuit board described inany one of the above-described [1] to [4], wherein the ground leadresidual portion is disposed on one surface in the thickness directionof the insulating layer.

According to such a configuration, since the ground lead residualportion is disposed on the insulating layer, it is possible to morereliably insulate the ground lead residual portion from the metalsupport layer.

The present invention [6] includes a method for producing a wiringcircuit board including the steps of preparing a metal support layer,forming an insulating layer on one side in a thickness direction of themetal support layer, forming a conductive layer including a terminalportion disposed on one side in the thickness direction of theinsulating layer, and a ground lead for electrically connecting theterminal portion to the metal support layer, subjecting the conductivelayer to electroless plating, and removing a portion of the ground leadso as to insulate the terminal portion from the metal support layer toform a ground lead residual portion, wherein a thickness of the groundlead residual portion is thinner than a thickness of the terminalportion.

According to such a method, after forming the conductive layer includingthe terminal portion, and the ground lead for electrically connectingthe terminal portion to the metal support layer, the conductive layer issubjected to electroless plating, and then, a portion of the ground leadis removed so as to insulate the terminal portion from the metal supportlayer to form the ground lead residual portion.

That is, when the conductive layer is subjected to electroless plating,since the ground lead electrically connects the terminal portion to themetal support layer, it is possible to form a uniform electrolessplating layer on the conductive layer. Further, since the thickness ofthe ground lead residual portion is thinner than that of the terminalportion, it is possible to smoothly remove the ground lead, and toimprove the connection reliability of a terminal.

The present invention [7] includes the method for producing a wiringcircuit board described in the above-described [6], wherein the step offorming the conductive layer includes the steps of simultaneouslyforming a lead forming layer constituting the ground lead, and aterminal forming layer constituting the terminal portion and continuouswith the lead forming layer, and forming the terminal forming layerconstituting the terminal portion without forming the lead forming layerconstituting the ground lead.

According to such a method, since the step of forming the conductivelayer includes the step of simultaneously forming the lead forming layerand the terminal forming layer, and the step of forming the terminalforming layer without forming the lead forming layer, the terminalportion consists of the plurality of terminal forming layers, and theground lead consists of the lead forming layer which has less numberthan the plurality of terminal forming layers.

Therefore, it is possible to reliably make the thickness of the groundlead thinner than that of the terminal portion, and thus, it is possibleto reliably make the thickness of the ground lead residual portionthinner than that of the terminal portion.

The present invention [8] includes the method for producing a wiringcircuit board described in the above-described [6] or [7], wherein inthe step of removing a portion of the ground lead, a portion of themetal support layer and a portion of the ground lead are simultaneouslyetched.

According to such a method, since a portion of the metal support layerand a portion of the ground lead are simultaneously etched, it ispossible to smoothly remove a portion of the ground lead, and to disposethe ground lead residual portion in the end portion of the wiringcircuit board. Further, since a portion of the metal support layer and aportion of the ground lead are simultaneously etched, as compared with acase of etching them separately, it is possible to decrease the numberof production steps.

The present invention [9] includes the method for producing a wiringcircuit board described in any one of the above-described [6] to [8]further including after the step of forming the insulating layer, andbefore the step of forming the conductive layer, a step of forming aseed film on one surface in the thickness direction of the insulatinglayer and on one surface in the thickness direction of the metal supportlayer exposed from the insulating layer; after the step of forming theconductive layer, and before the step of carrying out the electrolessplating, a step of removing the seed film exposed from the conductivelayer: and after the step of removing a portion of the ground lead, astep of removing the seed film exposed by the removal of the groundlead.

According to such a method, after forming the seed film on theinsulating layer and on the metal support layer exposed from theinsulating layer, the conductive layer is formed on the seed film,followed by subjecting the conductive layer to electroless plating toform the ground lead residual portion by removing a portion of theground lead, and then, the seed film exposed by the removal of theground lead is removed.

However, when the seed film exposed by the removal of the ground leadremains, there is a possibility that the ground lead residual portion iselectrically connected to the metal support layer via the seed film. Onthe other hand, according to the above-described method, since the seedfilm which is exposed by the removal of the ground lead is removed, itis possible to more reliably insulate the ground lead residual portionfrom the metal support layer.

Effect of the Invention

According to the wiring circuit board of the present invention, it ispossible to improve the connection reliability of a terminal portion,while forming a uniform electroless plating layer on a conductive layer.

Further, according to the method for producing a wiring circuit board ofthe present invention, it is possible to efficiently produce theabove-described wiring circuit board.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a plan view of a first embodiment of a wiring circuit boardof the present invention.

FIG. 2 shows an A-A cross-sectional view of the wiring circuit boardshown in FIG. 1.

FIGS. 3A to 3E show production process views of the wiring circuit boardshown in FIG. 2:

FIG. 3A illustrating a step of preparing a metal support layer.

FIG. 3B illustrating a step of forming a base insulating layer,

FIG. 3C illustrating a step of forming a seed film,

FIG. 3D illustrating a step of forming a first conductive layer, and

FIG. 3E illustrating a step of forming a second conductive layer.

FIGS. 4F to 4G show production process views of the wiring circuit boardsubsequent to FIG. 3E.

FIG. 4F illustrating a step of removing a seed film exposed from aconductive layer.

FIG. 4G illustrating a step of forming a first plating layer,

FIG. 4H illustrating a step of forming a cover insulating layer, and

FIG. 4I illustrating a step of removing the first plating layer exposedfrom the cover insulating layer.

FIGS. 5J to 5L show production process views of the wiring circuit boardsubsequent to FIG. 4I:

FIG. 5J illustrating a step of forming a ground lead residual portion,

FIG. 5K illustrating a step of removing a seed film exposed by formationof the ground lead residual portion, and

FIG. 5L illustrating a step of forming a second plating layer.

FIG. 6 shows a plan view of a conductive layer including a ground leadshown in FIG. 3E.

FIG. 7 shows a side cross-sectional view of a second embodiment of awiring circuit board of the present invention.

FIG. 8 shows a plan view of a third embodiment of a wiring circuit boardof the present invention.

FIG. 9 shows a B-B cross-sectional view of the wiring circuit boardshown in FIG. 8.

FIG. 10 shows a plan view of a conductive layer including a ground leadcorresponding to the ground lead residual portion shown in FIG. 8.

DESCRIPTION OF EMBODIMENTS First Embodiment

1. Wiring Circuit Board

A wiring circuit board 1 as a first embodiment of a wiring circuit boardof the present invention is described with reference to FIGS. 1 and 2.

As shown in FIGS. 1 and 2, the wiring circuit board 1 has a sheet shapehaving a thickness. The wiring circuit board 1 has, for example, arectangular shape w % ben in a plan view. Examples of the wiring circuitboard 1 include a flexible printed wiring board with a reinforcing layerincluding a metal support layer 2 as a reinforcing layer, and asuspension board with a circuit including the metal support layer 2 as asuspension (spring) layer.

Specifically, as shown in FIG. 2, the wiring circuit board 1 includesthe metal support layer 2, a base insulating layer 3 as one example ofan insulating layer, a seed film 6, a conductive layer 4, a firstplating layer 7, a cover insulating layer 5, and a second plating layer8.

The metal support layer 2 has a flat plate shape. A thickness of themetal support layer 2 is not particularly limited.

A material for the metal support layer 2 can be, for example,appropriately selected from a known or conventional metal-based material(specifically, a metal material). Specifically, examples of themetal-based material include metal elements classified in the group 1 togroup 16 in the periodic table, and alloys containing two or more metalelements. The metal element may be any of a transition metal and atypical metal.

More specifically, examples of the metal element include the group 2metal element such as calcium, the group 4 metal element such astitanium and zirconium, the group 5 metal element such as vanadium, thegroup 6 metal element such as chromium, molybdenum, and tungsten, thegroup 7 metal element such as manganese, the group 8 metal element suchas iron, the group 9 metal element such as cobalt, the group 10 metalelement such as nickel and platinum, the group 11 metal element such ascopper, silver, and gold, the group 12 metal element such as zinc, thegroup 13 metal element such as aluminum and gallium, and the group 14metal element such as germanium and tin.

These metal-based materials may be used alone or in combination of twoor more. Of the metal-based materials, preferably, an alloy containingtwo or more metal elements is used, more preferably, an alloy which canbe etched simultaneously with the conductive layer 4 is used,particularly preferably, an alloy containing stainless, steel, andcopper is used.

The base insulating layer 3 is disposed on one side in a thicknessdirection of the metal support layer 2, and specifically, on one surfacein the thickness direction of the metal support layer 2. The baseinsulating layer 3 has the same outer shape as the wiring circuit board1. The base insulating layer 3 has a thickness, and has flat one surfaceand the flat other surface in the thickness direction.

As shown in FIG. 1, the base insulating layer 3 includes a firstterminal disposed portion 30, a second terminal disposed portion 31, anda wiring disposed portion 32. The first terminal disposed portion 30 andthe second terminal disposed portion 31 are located at spaced intervalsto each other so as to sandwich the wiring disposed portion 32therebetween. The first terminal disposed portion 30 is continuous withthe wiring disposed portion 32. The first terminal disposed portion 30has a free end portion 30A located on the opposite side of the wiringdisposed portion 32. The free end portion 30A protrudes toward theopposite side of the wiring disposed portion 32 with respect to an endsurface 2A of the metal support layer 2 (ref: FIG. 2).

The second terminal disposed portion 31 is located on the opposite sideof the first terminal disposed portion 30 with respect to the wiringdisposed portion 32. The second terminal disposed portion 31 iscontinuous with the wiring disposed portion 32. Each of the firstterminal disposed portion 30 and the second terminal disposed portion 31is not covered with the cover insulating layer 5, and is exposed fromthe cover insulating layer 5. The wiring disposed portion 32C is locatedbetween the first terminal disposed portion 30 and the second terminaldisposed portion 31. The wiring disposed portion 32C is covered with thecover insulating layer 5.

Examples of a material for the base insulating layer 3 include resins(insulating resin materials) such as polyimide. A thickness of the baseinsulating layer 3 is not particularly limited, and is, for example, 1μm or more, and 1000 μm or less.

As shown in FIG. 2, the seed film 6 is disposed on one surface in thethickness direction of the base insulating layer 3. The seed film 6 hasa pattern corresponding to the conductive layer 4. Examples of amaterial for the seed film 6 include metals such as copper, chromium,and nickel, and alloys of these. The seed film 6 may be formed of onelayer, or two or more layers. A thickness of the seed film 6 is, forexample, 0.01 μm or more, and for example, 1 μm or less, preferably 0.1μm or less.

The conductive layer 4 is disposed on one side in the thicknessdirection of the base insulating layer 3, and specifically, on onesurface in the thickness direction of the seed film 6. As shown in FIG.1, the conductive layer 4 includes a ground pattern 10 and a pluralityof wiring patterns 11.

The ground pattern 10 includes a ground terminal 12 and a ground wiring13.

The ground terminal 12 is disposed on one side in the thicknessdirection of the first terminal disposed portion 30. Specifically, theground terminal 12 is disposed on one surface in the thickness directionof the first terminal disposed portion 30 via the seed film 6. Theground terminal 12 has a rectangular (square land) shape when extendingin a predetermined direction in a plan view.

The ground wiring 13 electrically connects the ground terminal 12 to themetal support layer 2. The ground wiring 13 is continuous from theground terminal 12 to extend from the first terminal disposed portion 30until the wiring disposed portion 32C. Specifically, the ground wiring13 is disposed over one surface in the thickness direction of the firstterminal disposed portion 30 and one surface in the thickness directionof the wiring disposed portion 32 via the seed film 6. The ground wiring13 penetrates through the wiring disposed portion 32C in the thicknessdirection to be grounded to the metal support layer 2. A dimension in awidth direction (direction perpendicular to a longitudinal direction) ofthe ground wiring 13 is smaller than that in the width direction(direction perpendicular to the longitudinal direction) of the groundterminal 12.

Each of the plurality of wiring patterns 11 includes a first terminal 15as one example of a terminal portion, a second terminal 16, a connectionwiring 17, and a ground lead residual portion 18. That is, theconductive layer 4 includes the plurality of first terminals 15, and theplurality of ground lead residual portions 18.

The first terminal 15 is disposed on one side in the thickness directionof the first terminal disposed portion 30. Specifically, the firstterminal 15 is disposed on one surface in the thickness direction of thefirst terminal disposed portion 30 via the seed film 6 (ref: FIG. 2).The first terminal 15 has a rectangular (square land) shape extending ina predetermined direction in a plan view. The plurality of firstterminals 15 and the ground terminal 12 are disposed at spaced intervalsto each other in the width direction (direction perpendicular to thelongitudinal direction) of the first terminal 15.

The second terminal 16 is disposed on one side in the thicknessdirection of the second terminal disposed portion 31. Specifically, thesecond terminal 16 is disposed on one surface in the thickness directionof the second terminal disposed portion 31 via the seed film 6. Thesecond terminal 16 has a rectangular (square land) shape extending in apredetermined direction in a plan view. The plurality of secondterminals 16 are disposed at spaced intervals to each other in the widthdirection (direction perpendicular to the longitudinal direction) of thesecond terminal 16.

The connection wiring 17 electrically connects the first terminal 15 tothe second terminal 16. The connection wiring 17 extends on the firstterminal disposed portion 30 continuously from the first terminal 15,then, passes over the wiring disposed portion 32C, and is connected tothe second terminal 16 on the second terminal disposed portion 31.Specifically, the connection wiring 17 is disposed over one surface inthe thickness direction of the first terminal disposed portion 30, onesurface in the thickness direction of the wiring disposed portion 32,and one surface in the thickness direction of the second terminaldisposed portion 31 via the seed film 6. A dimension in the widthdirection (direction perpendicular to the longitudinal direction) of theconnection wiring 17 is smaller than that in the width direction(direction perpendicular to the longitudinal direction) of the firstterminal 15.

The ground lead residual portion 18 is a residual portion of a groundlead 19 obtained by removing a portion of the ground lead 19 in a methodfor producing the wiring circuit board 1 to be described later (ref:FIG. 5). The ground lead residual portion 18 is disposed on one side inthe thickness direction of the first terminal disposed portion 30 (ref:FIG. 2). Specifically, the ground lead residual portion 18 is disposedon one surface in the thickness direction of the first terminal disposedportion 30 via the seed film 6. The ground lead residual portion 18 iselectrically connected to the first terminal 15. The ground leadresidual portion 18 is continuous from the first terminal 15 to extendtoward the opposite side of the connection wiring 17. The ground leadresidual portion 18 is located in the end portion of the wiring circuitboard 1. The ground lead residual portion 18 is located at the side ofthe first terminal 15 at spaced intervals thereto with respect to theend surface of the free end portion 30A of the first terminal disposedportion 30. That is, the free end portion 30A of the first terminaldisposed portion 30 protrudes toward the opposite side of the firstterminal 15 with respect to the ground lead residual portion 18 and themetal support layer 2 in a direction in which the ground lead residualportion 18 extends.

A thickness of the ground lead residual portion 18 is thinner than thatof the first terminal 15. When the thickness of the first terminal 15 isdefined as 100, the thickness of the ground lead residual portion 18 is,for example, 1 or more, preferably 5 or more, and for example, 90 orless, preferably 80 or less.

Specifically, the thickness of the ground lead residual portion 18 is,for example, 1 μm or more, and for example, 200 μm or less, preferably100 μm or less, further more preferably 50 μm or less. The thickness ofthe first terminal 15 is, for example, 10 μm or more, preferably 20 μmor more, and for example, 300 μm or less, preferably 200 μm or less.

As shown in FIG. 2, the conductive layer 4 consists of a plurality oflayers. In the present embodiment, the conductive layer 4 includes afirst conductive layer 40 and a second conductive layer 41. The numberof layers constituting the conductive layer 4 is not particularlylimited, and may be three or more.

The first conductive layer 40 is disposed on one surface in thethickness direction of the seed film 6. The first conductive layer 40includes a plurality of first terminal forming layers 42 as one exampleof a terminal forming layer, a plurality of lead forming layers 43, anda plurality of wiring forming layers 44.

The first terminal forming layer 42 constitutes the first terminal 15.The lead forming layer 43 is continuous with the first terminal forminglayer 42 to constitute the ground lead residual portion 18. The wiringforming layer 44 is continuous with the first terminal forming layer 42to constitute the connection wiring 17.

A thickness of the first conductive layer 40 is, for example, the sameas that of the ground lead residual portion 18 described above.

The second conductive layer 41 is disposed on one surface in thethickness direction of the first conductive layer 40. The secondconducive layer 41 includes a plurality of second terminal forminglayers 45 as one example of a terminal forming layer.

The second terminal forming layer 45 constitutes the first terminal 15.The second terminal forming layer 45 is disposed on one surface in thethickness direction of the first terminal forming layer 42. That is, thefirst terminal forming layer 42 and the second terminal forming layer 45are laminated in the thickness direction.

When the thickness of the first conductive layer 40 is defined as 100, athickness of the second conductive layer 41 is, for example, 1 or more,preferably 5 or more, and for example, 1000 or less, preferably 500 orless. Specifically, the thickness of the second conductive layer 41 is,for example, 1 μm or more, and for example, 200 μm or less, preferably100 μm or less.

Although not shown, the first conductive layer 40 further includes aground terminal forming layer constituting the ground terminal 12, aground wiring forming layer constituting the ground wiring 13, and athird terminal forming layer constituting the plurality of secondterminals 16.

In the present embodiment, as described above, the first terminal 15includes a plurality of first terminal forming layers laminated in thethickness direction (the first terminal forming layer 42 and the secondterminal forming layer 45), and preferably, consists of the firstterminal forming layer 42 and the second terminal forming layer 45. Thenumber of layers of the terminal forming layer provided in the firstterminal 15 is not particularly limited, and it may be three or more.

Further, the ground lead residual portion 18 includes the lead forminglayer 43 continuous with the first terminal forming layer 42, andpreferably, consists of the lead forming layer 43. The number of laversof the lead forming layer provided in the ground lead residual portion18 is not particularly limited as long as it is below the number oflayers of the terminal forming layer provided in the first terminal 15,and it may be two or more.

Further, the connection wiring 17 includes the wiring forming layer 44continuous with the first terminal forming layer 42, and preferably,consists of the wiring forming layer 44. The number of layers of thewiring forming layer provided in the connection wiring 17 is notparticularly limited, and it may be two or more.

Examples of a material for the conductive layer 4 (the first conductivelayer 40 and the second conductive layer 41) include metal elements suchas copper, silver, gold, iron, aluminum, and chromium, and metals suchas alloys containing two or more metal elements, and preferably, a metalcontaining copper such as copper and copper alloy is used.

The first plating layer 7 improves the adhesive properties between theconductive layer 4 and the cover insulating layer 5. The first platinglayer 7 is an electroless plating layer, and located between theconductive layer 4 and the cover insulating layer 5. Specifically, thefirst plating layer 7 is provided so as to cover the surfaces of theground wiring 13 and the connection wiring 17 located on the wiringdisposed portion 32. Examples of a material for the first plating layer7 include metal elements such as nickel, tin, silver, and palladium, andmetals such as alloys containing two or more metal elements, andpreferably, nickel is used. The first plating layer 7 may be formed ofone layer, or two or more layers. A thickness of the first plating layer7 is, for example, 0.01 μm or more, preferably 0.02 μm or more, and forexample, 1 μm or less, preferably 0.5 μm or less.

The cover insulating layer 5 is disposed on one surface in the thicknessdirection of the wiring disposed portion 32 so as to cover the groundwiring 13 and the connection wiring 17. Further, the cover insulatinglayer 5 exposes the ground terminal 12, the plurality of first terminals15, the plurality of ground lead residual portions 18, and the pluralityof second terminals 16 (ref: FIG. 1). An example of a material for thecover insulating layer 5 includes the same material for the baseinsulating layer 3. A thickness of the cover insulating layer 5 is notparticularly limited, and is, for example, 1 μm or more, and 1000 μm orless.

The second plating layer 8 is an electroless plating layer, and isprovided so as to cover the surface of the conductive layer 4 exposedfrom the cover insulating layer 5 (specifically, the ground terminal 12,the plurality of first terminals 15, the plurality of ground leadresidual portions 18, and the plurality of second terminals 16), and thesurface of the metal support layer 2. Examples of a material for thesecond plating layer 8 include metal elements such as nickel and gold,and alloys containing the metal elements. The second plating layer 8 maybe formed of one layer, or two or more layers. The second plating layer8 may be, for example, formed by laminating a first layer containingnickel and a second layer containing gold. A thickness of the secondplating layer 8 is, for example, 0.1 μm or more, preferably 0.25 μm ormore, and for example, 5 μm or less, preferably 2.5 μm or less.

2. Producing Method of Wiring Circuit Board

Next, a method for producing the wiring circuit board 1 is describedwith reference to FIGS. 3A to 6.

A method for producing the wiring circuit board 1 includes a step ofpreparing the metal support layer 2 (ref: FIG. 3A), a step of formingthe base insulating layer 3 (ref: FIG. 3B), a step of forming the seedfilm 6 (ref: FIG. 3C), a step of forming a conductive layer 4A (ref:FIGS. 3D and 3E), a step of removing the seed film 6 exposed from theconductive layer 4A (ref FIG. 4F), a step of forming the first platinglayer 7 (ref: FIG. 4G), a step of forming the cover insulating layer 5(ref: FIG. 4H), a step of removing the first plating layer 7 exposedfrom the cover insulating layer 5 (ref: FIG. 4I), a step of forming theground lead residual portion 18 (ref: FIG. 5J), a step of removing theseed film 6 exposed by the formation of the ground lead residual portion18 (ref: FIG. 5K), and a step of forming the second plating layer 8(ref: FIG. 5L).

As shown in FIG. 3A, first, the metal support layer 2 is prepared.

Then, as shown in FIG. 3B, the base insulating layer 3 is formed on oneside in the thickness direction of the metal support layer 2.Specifically, a varnish containing the above-described resin is appliedto one surface in the thickness direction of the metal support layer 2and dried to form a base film. Thereafter, the base film is exposed tolight via a photomask which is not shown to be developed, and cured byheating as necessary to form the base insulating layer 3 into theabove-described pattern.

In the base insulating layer 3, the free end portion 30A of the firstterminal disposed portion 30 is located inside the wiring circuit board1 with respect to the peripheral end surface of the metal support layer2. Therefore, a portion of one surface in the thickness direction of themetal support layer 2 is exposed from the base insulating layer 3. Inthe following, the portion of the metal support layer 2 exposed from thebase insulating layer 3 is referred to as a ground portion 20.

Then, as shown in FIG. 3C, the seed film 6 is formed on one surface inthe thickness direction of the base insulating layer 3, and on onesurface in the thickness direction of the ground portion 20 (the metalsupport layer 2 exposed from the base insulating layer 3). Examples of amethod for forming the seed film 6 include sputtering, electrolyticplating, and electroless plating, and preferably, sputtering is used.

Then, as shown in FIGS. 3D and 3E, the conductive layer 4A is formed onone surface in the thickness direction of the seed film 6. As shown inFIG. 6, the conductive layer 4A has the same configuration as that ofthe conductive layer 4, except that the plurality of ground leads 19 areprovided instead of the plurality of ground lead residual portions 18.In the following, the conductive layer 4A including the ground lead 19is distinguished from the conductive layer 4 including the ground leadresidual portion 18 as a pre-conductive layer 4A.

The ground lead 19 electrically connects the first terminal 15 to theground portion 20. The ground lead 19 is continuous from the firstterminal 15 to extend toward the opposite side of the connection wiring17, and passes over the free end portion 30A of the first terminaldisposed portion 30 to be located on the ground portion 20. The groundlead 19 is located in the end portion of the pre-conductive layer 4A.The ground lead 19 includes a first portion 19A and a second portion19B.

The first portion 19A is located on one side in the thickness directionof the first terminal disposed portion 30, and in particular, disposedon one surface in the thickness direction of the first terminal disposedportion 30 via the seed film 6 (ref: FIG. 3E). The first portion 19A iscontinuous with the first terminal 15. The second portion 19Belectrically connects the first portion 19A to the ground portion 20.The second portion 19B is continuous with the first portion 19A, andlocated on one side in the thickness direction of the ground portion 20.Specifically, the second portion 19B is in contact with one surface inthe thickness direction of the ground portion 20 via the seed film 6(ref: FIG. 3E).

To form the pre-conductive layer 4A, as shown in FIGS. 3D and 3E, afterforming the first conductive layer 40A on one surface in the thicknessdirection of the seed film 6, the second conductive layer 41 is formedon one surface in the thickness direction of the first conductive layer40A.

To form the first conductive layer 40A, though not shown, a resisthaving a reversed pattern of the first conductive layer 40A is disposedon the seed film 6 to be subjected to, for example, electrolytic plating(preferably, electrolytic copper plating). Thereafter, the resist isremoved.

The first conductive layer 40A has the same configuration as that of thefirst conductive layer 40, except that it includes a plurality of leadforming layers 46 instead of the plurality of lead forming layers 43.The lead forming layer 46 is continuous with the first terminal forminglayer 42 to constitute the ground lead 19. In other words, in theformation of the first conductive layer 40A, the lead forming layer 46constituting the ground lead 19, and the first terminal forming layer 42constituting the first terminal 15 and continuous with the lead forminglayer 46 are simultaneously formed.

Then, as shown in FIG. 3E, the second conductive layer 41 is formed. Toform the second conductive layer 41, though not shown, a resist having areversed pattern of the second conductive layer 41 is disposed on thefirst conductive layer 40A to be subjected to, for example, electrolyticplating (preferably, electrolytic copper plating). Thereafter, theresist is removed.

Thus, the second terminal forming layer 45 constituting the firstterminal 15 is formed without forming the lead forming layerconstituting the ground lead 19. The second terminal forming layer 45 isformed on one surface in the thickness direction of the first terminalforming layer 42, and the first terminal 15 is formed.

Thus, the pre-conductive layer 4A including the first terminal 15 andthe ground lead 19 is formed.

Then, as shown in FIG. 4F, the seed film 6 exposed from thepre-conductive layer 4A is removed by known etching (for example, wetetching and the like). Examples of an etching solution of the seed film6 include a caustic soda aqueous solution, a potassium permanganatesolution, and a sodium metasilicate solution.

Then, as shown in FIG. 4G the pre-conductive layer 4A is subjected toelectroless plating using a first electroless plating solutioncontaining metal ions (for example, nickel ions) of the material for thefirst plating layer 7 described above.

Thus, the first plating layer 7 is formed so as to cover the exposedpre-conductive layer 4A (the ground terminal 12, the ground wiring 13,the first terminal 15, the second terminal 16, the connection wiring 17,and the ground lead 19).

Next, as shown in FIG. 4H, the cover insulating layer 5 is formed on oneside in the thickness direction of the base insulating layer 3,specifically, on one surface in the thickness direction of the wiringdisposed portion 32 so as to cover the ground wiring 13 and theconnection wiring 17. The cover insulating layer 5 is formed into theabove-described pattern.

Specifically, a varnish containing the above-described resin is appliedto one surface in the thickness direction of the base insulating layer 3and dried to form a cover film. Thereafter, the cover film is exposed tolight via a photomask which is not shown to be developed, and cured byheating as necessary to form the cover insulating layer 5 into theabove-described pattern.

Then, as shown in FIG. 4I, the first plating layer 7 exposed from thecover insulating layer 5 is removed by known etching (for example, wetetching and the like). Examples of an etching solution of the firstplating layer 7 include sulfuric acid and hydrogen peroxide, andpemitric acid water.

Next, as shown in FIG. 5J, the ground portion 20 of the metal supportlayer 2 and the second portion 19B of the ground lead 19 aresimultaneously etched so that the first terminal 15 is insulated fromthe metal support layer 2 to remove a portion of the ground lead 19.Specifically, the ground portion 20 and the second portion 19B aresimultaneously removed by wet etching. An example of an etching solutionincludes a ferric chloride solution.

At this time, after removing the ground portion 20, the etching solutionfurther etches the metal support layer 2 so that the end surface 2A ofthe metal support layer 2 is located on the side of the first terminal15 with respect to the free end portion 30A of the first terminaldisposed portion 30. Also, after removing the second portion 19B, theetching solution further etches the ground lead 19 until the end surfaceof the first portion 19A is located on the side of the first terminal 15with respect to the free end portion 30A.

Thus, the ground lead residual portion 18 is formed, and the free endportion 30A of the first terminal disposed portion 30 protrudes towardthe opposite side of the first terminal 15 with respect to the groundlead residual portion 18 and the metal support layer 2.

Next, as shown in FIG. 5K, the seed film 6 exposed by removal of theground lead 19 is removed. Specifically, the seed film 6 located on thefree end portion 30A is removed by known etching (for example, wetetching and the like).

Then, as shown in FIG. 5L, the conductive layer 4 exposed from the coverinsulating layer 5 (specifically, the ground terminal 12, the firstterminal 15, the ground lead residual portion 18, and the secondterminal 16) and the metal support layer 2 are subjected to electrolessplating using a second electroless plating solution containing the metalions of the material for the second plating layer 8 described above.When the second plating layer 8 is formed of a plurality of layers, theelectroless plating is repeated. For example, after the electrolessplating using the second electroless plating solution containing thefirst metal ions (for example, nickel ions), the electroless plating iscarried out using the second electroless plating solution containing thesecond metal ions (for example, gold ions).

Thus, the second plating layer 8 is formed so as to cover the exposedconductive layer 4 (specifically, the ground terminal 12, the firstterminal 15, the ground lead residual portion 18, and the secondterminal 16) and the metal support layer 2.

Thus, the wiring circuit board 1 is produced.

The application of the wiring circuit board 1 is not particularlylimited, and the wiring circuit board 1 is used in various fields. Thewiring circuit board 1 is, for example, used for various applicationssuch as a wiring circuit board for an electronic device (wiring circuitboard for an electronic component) and a wiring circuit board for anelectric device (wiring circuit board for an electric component).Examples of the wiring circuit board for an electronic device and thewiring circuit board for an electric device include a wiring circuitboard for a sensor used for sensors such as a position informationsensor, an obstacle detection sensor, and a temperature sensor; a wiringcircuit board for a transport vehicle used for transport vehicles suchas an automobile, a train, an aircraft, and a working vehicle; a wiringcircuit board for a video device used for video devices such as a flatpanel display, a flexible display, and a projection video device; awiring circuit board for a communication relay device used forcommunication relay devices such as a network device and a largecommunication device; a wiring circuit board for an informationprocessing terminal used for information processing terminals such as acomputer, a tablet, a smartphone, and a video game; a wiring circuitboard for a movable device used for movable devices such as a drone anda robot; a wiring circuit board for medical equipment used for medicalequipments such as wearable medical equipment and medical diagnosticequipment; a wiring circuit board for an electric device used forelectric devices such as a refrigerator, a washing machine, a vacuumcleaner, and an air conditioning machine; and a wiring circuit board fora recording electronic device used for recording electronic devices suchas a digital camera and a DVD recording device.

As shown in FIG. 1, the ground lead residual portion 18 is formed byremoving a portion of the ground lead 19 for electrically connecting thefirst terminal 15 to the metal support layer 2 in the production of thewiring circuit board 1 (ref: FIG. 53). Therefore, before removing theground lead 19, since the first terminal 15 is electrically connected tothe metal support layer 2, it is possible to uniformly form the firstplating layer 7 on the conductive layer 4.

Further, as shown in FIG. 2, the thickness of the ground lead residualportion 18 is thinner than that of the first terminal 15. Therefore, itis possible to smoothly remove the ground lead 19.

A method for etching a portion of the ground lead 19 is not particularlylimited, and it may be wet etching or dry etching. However, in a casewhere a portion of the ground lead 19 is removed by wet etching, whenthe thickness of the ground lead residual portion 18 is not less thanthat of the first terminal 15, a portion of the ground lead 19 may notbe sufficiently removed.

In this regard, in the wiring circuit board 1, since the thickness ofthe ground lead residual portion 18 is thinner than that of the firstterminal 15, it is also possible to reliably remove a portion of theground lead 19 by wet etching, and to suppress the erosion of the firstterminal 15 by over-etching, and thus, it is possible to improve theconnection reliability of the first terminal 15.

As shown in FIG. 2, the first terminal 15 includes the first terminalforming layer 42 and the second terminal forming layer 45, and theground lead residual portion 18 includes the lead forming layer 43continuous with the first terminal forming layer 42. Therefore, it ispossible to reliably make the thickness of the ground lead residualportion 18 thinner than that of the first terminal 15. Further, sincethe first terminal forming layer 42 and the lead forming layer 43 arecontinuous with each other, it is possible to improve the reliability ofthe electrical conduction between the first terminal forming layer 42and the lead forming layer 43.

As shown in FIG. 1, the ground lead residual portion 18 is located inthe end portion of the wiring circuit board 1. Therefore, in theproduction of the wiring circuit board 1, it is possible to moresmoothly remove a portion of the ground lead 19, and to form the groundlead residual portion 18.

As shown in FIG. 2, the ground lead residual portion 18 is disposed onthe first terminal disposed portion 30, and the free end portion 30A ofthe first terminal disposed portion 30 protrudes toward the oppositeside of the first terminal 15 with respect to the ground lead residualportion 18 and the metal support layer 2 in a direction in which theground lead residual portion 18 extends. Therefore, it is possible toreliably insulate the ground lead residual portion 18 from the metalsupport layer 2.

Further, as shown in FIGS. 4F to 5J, in the method for producing thewiring circuit board 1, after forming the pre-conductive layer 4Aincluding the first terminal 15 and the ground lead 19 (ref: FIG. 4F),the pre-conductive layer 4A is subjected to electroless plating (ref:FIG. 4G), and then, the second portion 19B of the ground lead 19 isremoved so that the first terminal 15 is insulated from the metalsupport layer 2 to form the ground lead residual portion 18 (ref: FIG.5J).

That is, when the pre-conductive layer 4A is subjected to electrolessplating, since the ground lead 19 electrically connects the firstterminal 15 to the metal support layer 2, it is possible to form theuniform first plating layer 7 on the pre-conductive layer 4A. Further,since the thickness of the ground lead residual portion 18 is thinnerthan that of the first terminal 15, it is possible to improve theconnection reliability of the first terminal 15, while smoothly removingthe ground lead 19.

Further, as shown in FIGS. 3D and 3E, the step of forming the conductivelayer 4 includes the step of simultaneously forming the lead forminglayer 46 and the first terminal forming layer 42, and the step offorming the second terminal forming layer 45 without forming the leadforming layer. Therefore, the first terminal 15 consists of a pluralityof terminal forming layers, and the ground lead 19 consists of leadforming layers which has less number than the plurality of terminalforming layers. Therefore, it is possible to reliably make the thicknessof the ground lead 19 thinner than that of the first terminal 15, andthus, to reliably make the thickness of the ground lead residual portion18 thinner than that of the first terminal 15.

Further, as shown in FIG. 5J, the ground portion 20 of the metal supportlayer 2 and the second portion 19B of the ground lead 19 aresimultaneously etched. Therefore, it is possible to smoothly remove thesecond portion 19B of the ground lead 19, and to dispose the ground leadresidual portion 18 in the end potion of the wiring circuit board 1, andit is possible to decrease the number of production steps. It is alsopossible to separately carry out the etching of the metal support layer2, and the etching of the ground lead 19.

Further, as shown in FIG. 5K, the seed film 6 exposed by the removal ofthe ground lead 19 is removed. Therefore, it is possible to morereliably insulate the ground lead residual portion 18 from the metalsupport layer 2.

Second Embodiment

Next, a second embodiment of the wiring circuit board of the presentinvention is described with reference to FIG. 7. In the secondembodiment, the same reference numerals are provided for memberscorresponding to each of those in the above-described first embodiment,and their detailed description is omitted.

In the above-described first embodiment, as shown in FIG. 2, the firstconductive layer 40 includes the first terminal forming layer 42, thelead forming layer 43, and the wiring forming layer 44, and the secondconductive layer 41 includes the second terminal forming layer 45.However, the configuration of the conductive layer 4 is not limited tothis.

In the second embodiment, as shown in FIG. 7, the first conductive layer40 includes the first terminal forming layer 42, and the secondconductive layer 41 includes the second terminal forming layer 45, thelead forming layer 43, and the wiring forming layer 44. In this case,the lead forming layer 43 is continuous with the second terminal forminglayer 45 without being continuous with the first terminal forming layer42. The wiring forming layer 44 is continuous with the second terminalforming layer 45 without being continuous with the first terminalforming layer 42.

In the second embodiment, the same function and effect as that of theabove-described first embodiment can be achieved.

Third Embodiment

Next, a third embodiment of the wiring circuit board of the presentinvention is described with reference to FIGS. 8 and 9. In the thirdembodiment, the same reference numerals are provided for memberscorresponding to each of those in the above-described first embodiment,and their detailed description is omitted.

In the above-described first embodiment, as shown in FIG. 2, the groundlead residual portion 18 consists of only a portion to be continuouswith the first terminal 15. However, the configuration of the groundlead residual portion is not limited to this.

In the third embodiment, as shown in FIG. 8, the ground lead residualportion 22 includes a first residual portion 22A and a second residualportion 22B.

As shown in FIG. 9, the first residual portion 22A is disposed on oneside in the thickness direction of the first terminal disposed portion30. Specifically, the first residual portion 22A is disposed on onesurface in the thickness direction of the first terminal disposedportion 30 via the seed film 6. The first residual portion 22A iselectrically connected to the first terminal 15. The first residualportion 22A is continuous from the first terminal 15 to extend towardthe opposite side of the connection wiring 17.

The second residual portion 22B is located at the opposite side of thefirst terminal 15 with respect to the first residual portion 22A atspaced intervals thereto. The second residual portion 22B iselectrically connected to the metal support layer 2 via a through hole33 provided in the first terminal disposed portion 30. Specifically, thesecond residual portion 22B fills the through hole 33 and is in contactwith one surface in the thickness direction of the metal support layer 2via the seed film 6.

To produce the wiring circuit board 1 of the third embodiment, apre-conductive layer 4B including the first terminal 15 and a groundlead 21 is formed in the same manner as in the first embodiment. Asshown in FIG. 10, the ground lead 21 has a first portion 21Acorresponding to the first residual portion 22A, and a second portion21B corresponding to the second residual portion 22B. The first portion21A connects the first terminal 15 to the second portion 21B.

Then, after the electroless plating of the pre-conductive layer 4B toform the first plating layer 7 in the same manner as in the firstembodiment (ref: FIG. 4G), the cover insulating layer 5 is formed (ref:FIG. 4H), next, the first plating layer 7 exposed from the coverinsulating layer 5 is removed (ref: FIG. 4I), and thereafter, as shownin FIG. 8, a portion between a continuous portion from the first portion21A and the second portion 21B in the ground lead 21 is removed to fromthe ground lead residual portion 22. Therefore, the first residualportion 22A continuous with the first terminal 15 is not located in theend portion of the wiring circuit board 1. Thereafter, as shown in FIG.9, the seed film 6 exposed by removal of the ground lead 21 is removed,and then, the second plating layer 8 is formed in the exposed conductivelayer 4.

Thus, the wiring circuit board 1 of the third embodiment is produced.

In the third embodiment, the same function and effect as that of theabove-described first embodiment can be achieved. On the other hand, inthe third embodiment, a portion of the seed film 6 may remain betweenthe first residual portion 22A and the second residual portion 22B.Therefore, from the viewpoint of ensuring insulating properties of thefirst terminal 15 and the metal support layer 2, the first embodimentand the second embodiment are more preferable than the third embodiment.

MODIFIED EXAMPLES

In the above-described first to third embodiments, as shown in FIGS. 41and 5J, after the removal of the first plating layer 7 exposed from thecover insulating layer 5, a portion of the ground lead 19 is removed.However, the order of the removal of the first plating layer and theremoval of the ground lead is not limited to this. After the removal ofa portion of the ground lead, the first plating layer exposed from thecover insulating layer may be also removed.

In the above-described first to third embodiments, as shown in FIG. 5L,the second plating layer 8 is formed by electroless plating. However, amethod for forming the second plating layer is not limited to this. Forexample, after the removal of the first plating layer and before theremoval of a portion of the ground lead, it is also possible to form thesecond plating layer by electroless plating using the ground lead as aplating lead (ref: FIG. 4I).

In the above-described first to third embodiments, the first terminalconsists of a plurality of terminal forming layers, and the ground leadresidual portion consists of the lead forming layer which has lessnumber than the plurality of terminal forming layers. Alternatively,also, the first terminal may consist of one terminal forming layer, andthe ground lead residual portion may consist of one lead forming layercontinuous with the terminal forming layer. In this case, the groundlead residual portion is, for example, formed thinner than the firstterminal by etching.

In addition, in the above-described first to third embodiments, theconductive layer is formed by an additive method of forming a conductivelayer on a seed film after forming the seed film. However, a method forforming the conductive layer is not limited to this. The conductivelayer may be also formed by a subtractive method.

The modified examples can achieve the same function and effect as thatof the above-described first embodiment. Further, the first to the thirdembodiments and the modified examples can be appropriately used incombination.

While the illustrative embodiments of the present invention are providedin the above description, such is for illustrative purpose only and itis not to be construed as limiting the scope of the present invention.Modification and variation of the present invention that will be obviousto those skilled in the art is to be covered by the following claims.

INDUSTRIAL APPLICATION

The wiring circuit board of the present invention is, for example, usedfor various applications such as a wiring circuit board for anelectronic device (wiring circuit board for an electronic component),and a wiring circuit board for an electric device (wiring circuit boardfor an electric component).

DESCRIPTION OF REFERENCE NUMERALS

-   -   1 Wiring circuit board    -   2 Metal support layer    -   3 Base insulating layer    -   4 Conductive layer    -   4A Pre-conductive layer    -   4B Pre-conductive layer    -   6 Seed film    -   15 First terminal    -   18 Ground lead residual portion    -   19 Ground lead    -   21 Ground lead    -   22 Ground lead residual portion    -   40 First conductive layer    -   41 Second conductive layer    -   42 First terminal forming layer    -   43 Lead forming layer    -   45 Second terminal forming layer    -   46 Lead forming layer

1. A wiring circuit board comprising: a metal support layer, aninsulating layer disposed on one side in a thickness direction of themetal support layer, and a conductive layer disposed on one side in thethickness direction of the insulating layer, and including a terminalportion and a ground lead residual portion electrically connected to theterminal portion, wherein a thickness of the ground lead residualportion is thinner than a thickness of the terminal portion.
 2. Thewiring circuit board according to claim 1, wherein the terminal portionincludes a plurality of terminal forming layers laminated in thethickness direction, and the ground lead residual portion includes alead forming layer continuous with at least one of the plurality ofterminal forming layers.
 3. The wiring circuit board according to claim1, wherein the ground lead residual portion is located in an end portionof the wiring circuit board.
 4. The wiring circuit board according toclaim 1, wherein a portion of the insulating layer protrudes toward theopposite side of the terminal portion with respect to the ground leadresidual portion and the metal support layer in a direction in which theground lead residual portion extends.
 5. The wiring circuit boardaccording to claim 1, wherein the ground lead residual portion isdisposed on one surface in the thickness direction of the insulatinglayer.
 6. A method for producing a wiring circuit board comprising thesteps of: preparing a metal support layer, forming an insulating layeron one side in a thickness direction of the metal support layer, forminga conductive layer including a terminal portion disposed on one side inthe thickness direction of the insulating layer, and a ground lead forelectrically connecting the terminal portion to the metal support layer,subjecting the conductive layer to electroless plating, and removing aportion of the ground lead so as to insulate the terminal portion fromthe metal support layer to form a ground lead residual portion, whereina thickness of the ground lead residual portion is thinner than athickness of the terminal portion.
 7. The method for producing a wiringcircuit board according to claim 6, wherein the step of forming theconductive layer includes the steps of: simultaneously forming a leadforming layer constituting the ground lead, and a terminal forming layerconstituting the terminal portion and continuous with the lead forminglayer, and forming the terminal forming layer constituting the terminalportion without forming the lead forming layer constituting the groundlead.
 8. The method for producing a wiring circuit board according toclaim 6, wherein in the step of removing a portion of the ground lead, aportion of the metal support layer and a portion of the ground lead aresimultaneously etched.
 9. The method for producing a wiring circuitboard according to claim 6 further comprising: after the step of formingthe insulating layer, and before the step of forming the conductivelayer, a step of forming a seed film on one surface in the thicknessdirection of the insulating layer and on one surface in the thicknessdirection of the metal support layer exposed from the insulating layer;after the step of forming the conductive layer, and before the step ofcarrying out the electroless plating, a step of removing the seed filmexposed from the conductive layer; and after the step of removing aportion of the ground lead, a step of removing the seed film exposed bythe removal of the ground lead.